docs: def _canonicalize(self, expression):
          """For example, changes x + y to 1.*x + 1.*y"""
          expression = super(Objective, self)._canonicalize(expression)
          if isinstance(expression, sympy.Basic):
              expression *= 1.
          else:  # pragma: no cover   # symengine
              expression = (1. * expression).expand()
          return expression